Light source lighting circuit and turn signal lamp

Cross-reference to related application

The present application claims the benefit of priority of Japanese Patent Applications No. 2014-260986, filed on Dec. 24, 2014, No. 2014-260987, filed on Dec. 24, 2014, No. 2014-264284, filed on Dec. 26, 2014 and No. 2015-090386, filed on Apr. 27, 2015, the disclosures of which are incorporated herein by reference.

Technical field

The present invention relates to a technology field of a light source lighting circuit configured to turn on a light source on the basis of electric power supplied from a vehicle-side and a turn signal lamp having the light source lighting circuit and the light source.

Related art

As a vehicle lamp, a turn signal lamp configured to function as a direction indicator has been known. The turn signal lamp includes a left and front turn signal lamp and a right and front turn signal lamp provided at left and right sides of a front end portion of a vehicle and a left and rear turn signal lamp and a right and rear turn signal lamp provided at left and right sides of a rear end portion of the vehicle, and is ON/OFF controlled by a predetermined in-vehicle ECU (Electronic Control Unit) such as a meter ECU, in response to operations of a winker lever, a hazard switch and the like by a driver.

An ECU having four ports for supplying electric power to the four turn signal lamps has been known. In this case, the ECU is configured to individually determine whether there is disconnection for each of the four turn signal lamps. The disconnection determination is performed by determining whether a supply current value is below a predetermined threshold value, for each port.

Regarding the disconnection determination for the turn signal lamp, Patent Document 1 discloses a technology for diverting a determination threshold value for a turn signal lamp in which an incandescent lamp is a light source, to a turn signal lamp in which an LED (light emitting diode) is a light source. Specifically, Patent Document 1 discloses a technology of connecting an electric power consuming unit to a port of an ECU in parallel with the LED and reducing power consumption of the electric power consuming unit when disconnection of the LED is detected. Since the power consumption of the LED is less than the incandescent lamp, the supply current value through the port is smaller, as compared to a case where the incandescent lamp is used. For this reason, when the LED is used, a difference between the supply current values of the port in a normal state where the disconnection does not occur and in a disconnection state is small, so that it is not possible to appropriately determine whether or not the disconnection if the determination threshold value for incandescent lamp is used, as it is (it is erroneously determined that the disconnection is normal). Therefore, in the normal state where the disconnection does not occur, load current is enabled to flow in a pseudo manner by the electric power consuming unit, so that the supply current value from the port is made to be equivalent to the case where the incandescent lamp is used, and upon the disconnection, the power consumption by the electric power consuming unit is reduced to highly lower the supply current value from the port, so that the difference between the supply current values in the normal state and in the disconnection state is made to be equivalent to the case where the incandescent lamp is used. Thereby, the disconnection determination where the determination threshold value for incandescent lamp is used as it is can be performed.

Also, Patent Document 2 discloses a technology of enabling an the electric power consuming unit (a pseudo-load unit) to consume electric power in a normal state and to reduce power consumption of a current consuming unit in a disconnection state for the purpose of diversion of a disconnection determination threshold value for incandescent lamp when an LED is used as a light source, like Patent Document 1. Patent Document 2 discloses that a plurality of LEDs is provided and the power consumption of the electric power consuming unit is reduced when the disconnection is detected for any one LED.

According to the above related art, when changing the turn signal lamp from the incandescent lamp to the LED, it is possible to divert the ECU for performing the disconnection determination, as it is. Therefore, when it is intended to reduce the power consumption of the turn signal lamp, it is possible to suppress the cost-up.

Also, as the turn signal lamp, for example, Patent Document 3 and Patent Document 4 disclose a turn signal lamp in which a plurality of light sources aligned from an inner side to an outer side in a width direction of a vehicle is sequentially turned on, which is a sequential lighting. SUMMARY OF THE INVENTION Problems to be Solved

For example, when changing a model of the vehicle, an ECU in which a threshold value for LED is set as the disconnection determination threshold value may be newly mounted. When the threshold value for LED is used, it is not necessary to make the supply current value from the port equivalent to the case where the incandescent lamp is used. Therefore, it is considered that it is not necessary to provide the pseudo-load such as the electric power consuming unit upon the disconnection determination.

However, even when the threshold value for LED is used, it may not possible to appropriately perform the disconnection determination, depending on the configuration of the turn signal lamp. Specifically, the turn signal lamp, particularly, the left and rear turn signal lamp and the right and rear turn signal lamp to be arranged at the rear side may be dispersedly formed in two housings, not one housing. In other words, one set of the two lamp units configures each of the left and rear turn signal lamp and the right and rear turn signal lamp. In this case, since light emitting units are respectively arranged in the separate lamp units, lighting circuits of the light emitting units are also arranged in the separate lamp units, respectively.

In the above case, when the ECU having the four ports is used, each of the two ports allotted to the rear side supplies the electric power to the two lamp units (the lighting circuits). In other words, the two lamp units of each turn signal lamp are supplied with the electric power by commonly using one corresponding port.

In this case, the ECU determines that there is disconnection if any one of the two lamp units configuring each of the left and rear turn signal lamp and the right and rear turn signal lamp is disconnected. Specifically, the ECU determines whether each turn signal lamp is disconnected by determining whether the supply current values from the left and rear port and the right and rear port are below the threshold value, which is set in correspondence to the supply current value when one lamp unit is disconnected.

At this time, however, it should be noted that the supply current value from the port is not constant, i.e., may fluctuate depending on fluctuation in an input voltage from an in-vehicle battery or may be varied due to the other causes. Due to the fluctuation and variation, a lower limit value of the supply current value in the normal state where the disconnection does not occur and an upper limit value of the supply current value in the disconnection state of one lamp unit may come close to each other or lap each other (i.e., the values may become the same value or the relation of the upper and lower limit values may be reversed). In the case where the values lap each other, it is not possible to perform the disconnection determination even when any threshold value is set. Also, in the case where the values come close to each other, it is not possible to perform the disconnection determination if a difference between the two values is small. In order to perform the disconnection determination by using the threshold value, the difference between both the values, which are comparison targets, is required to be equal or larger than a predetermined value, based on the detection precision of the supply current value. Therefore, when the values come close to each other in such a level that the difference is less than the predetermined value, both the values are detected as the same value, so that it is not possible to appropriately perform the disconnection determination.

Like this, according to the configuration where the turn signal lamp consists of the two lamp units and the lighting circuits provided in the respective lamp units are supplied with the electric power from one common port of the ECU, it may not be possible to appropriately perform the disconnection determination even when any determination threshold value is set.

It is therefore a first object of the present invention to appropriately perform disconnection determination for a vehicle lamp provided with a first lamp unit and a second lamp unit each of which is configured to receive electric power supply from a common electric power supply line.

Also, a turn signal lamp, particularly, a left and rear turn signal lamp and a right and rear turn signal lamp to be arranged at a rear side may be dispersedly formed in two housings, not one housing, and light emitting units thereof may be dispersedly arranged in separate housings, respectively.

Like this, in each of the left and rear turn signal lamp and the right and rear turn signal lamp of which the light emitting units are dispersedly arranged in the separate housings, sequential lighting is performed in order from a light emitting unit (hereinafter, referred to as “first light emitting unit”) arranged closely to an inner side of a vehicle to a light emitting unit (hereinafter, referred to as “second light emitting unit”) arranged closely to an outer side of the vehicle. Specifically, after light sources aligned in the first light emitting unit are sequentially turned on in a direction from the inner side towards the outer side of the vehicle, a light source in the second light emitting unit is turned on.

In order to implement the above sequential lighting, it is considered to provide a lighting circuit of the first light emitting unit with a timing generation circuit (timer circuit) for sequentially turning on the light sources at a predetermined time interval and to provide a lighting circuit of the second light emitting unit with a timing generation circuit for standing by for a time period until all the light sources of the first light emitting unit are turned on.

However, when each lighting circuit is provided with the timing generation circuit, a deviation may be caused with respect to connection of the sequential lighting from the first light emitting unit to the second light emitting unit due to variation in characteristics of each timing generation circuit.

It is therefore a second object of the present invention to prevent deviation in connection of the sequential lighting from the first light emitting unit to the second light emitting unit.

Also, like hazard lighting of a vehicle lamp, for example, the turn signal lamp, a pair of lamps of which electric power supply from the vehicle-side is individually controlled may repeat simultaneous lighting with a relatively short period.

The hazard lighting may be continued for a relatively long time period during stop of the vehicle, for example. In particular, it can be said that the tendency increases in a commercial vehicle such as a truck.

As described above, in the lamp having the electric power consuming unit so as to cope with the ECU of the related art based on the assumption of the incandescent lamp, when the hazard lighting is continued for a relatively long time period at a state where an engine stops, for example, a possibility that a battery will be dead increases. In addition to this, since an amount of heat generation may be excessively increased in the lamp, it is required to take measures against the heat in the lamp, which increases the cost.

It is therefore a third object of the present invention to perform disconnection determination upon lighting of one lamp for a pair of lamps of which electric power supply from a vehicle-side is individually controlled, to reduce power consumption and an amount of heat generation when both lamps are turned on, to decrease a possibility that a battery will be dead in the vehicle, and to reduce the manufacturing cost of the lamp. Means for Solving Problems

A light source lighting circuit of the first invention for achieving the first object is a light source lighting circuit provided with a first lighting circuit configured to receive current from an electric power supply line and to supply drive current to a first light source and a second lighting circuit configured to receive current from the electric power supply line and to supply drive current to a second light source. The first lighting circuit is configured to generate a first state signal corresponding to a state of the drive current flowing to the first light source and to output a second notification signal corresponding to the first state signal to the second lighting circuit, and the second lighting circuit is configured to generate a second state signal corresponding to a state of the drive current flowing to the second light source and to output a first notification signal corresponding to the second state signal to the first lighting circuit. When the first state signal indicates an abnormality or when the first notification signal indicates an abnormality, the first lighting circuit stops operation thereof. When the second state signal indicates an abnormality or when the second notification signal indicates an abnormality, the second lighting circuit stops operation thereof.

With this configuration, when disconnection occurs in at least one of the first light source and the second light source, both the first lighting circuit and the second lighting circuit stop operations thereof. In other words, when disconnection occurs in at least one of the first light source and the second light source, the supply current to the light source lighting circuit becomes substantially zero (0), so that a difference between supply current values in a normal state and in the disconnection state increases.

In the light source lighting circuit of the first invention, the first lighting circuit may include a current consuming unit configured to enable regulating current to flow by consuming a part of the electric power to be supplied from the electric power supply line, and may reduce a current value of the regulating current when the first state signal indicates an abnormality or when the first notification signal indicates an abnormality.

With the configuration, the supply current value of the electric power supply line is increased in the normal state.

In the light source lighting circuit of the first invention, preferably, the first lighting circuit includes a first DC/DC converter having a first switching element, and the second lighting circuit includes a second DC/DC converter having a second switching element.

The DC/DC converter has a relatively less amount of heat generation.

Also, a turn signal lamp of the first invention includes a first lamp unit attached to a door part provided to be freely openable and closable for a vehicle main body part at a rear end portion of a vehicle, and a second lamp unit attached to the vehicle main body part-side and positioned at an outermore side than the first lamp unit in a width direction of the vehicle. The first lamp unit includes a first light emitting unit and the first lighting circuit of the light source lighting circuit of the first invention, and the second lamp unit includes a second light emitting unit and the second lighting circuit of the light source lighting circuit of the first invention.

With this configuration, it is possible to appropriately perform the disconnection determination for the turn signal lamp in which the respective lamp units are dispersedly arranged at the vehicle main body part and the door part.

A light source lighting circuit of the second invention for achieving the second object is a light source lighting circuit provided with a first lighting circuit configured to turn on a plurality of light sources of a first light emitting unit on the basis of an input voltage and a second lighting circuit configured to turn on a light source of the second light emitting unit on the basis of an input voltage. The first lighting circuit is configured to sequentially turn on the light sources of the first light emitting unit in accordance with a timing signal and to output the timing signal to the second lighting circuit, and the second lighting circuit is configured to start lighting of the light source of the second light emitting unit in accordance with the timing signal.

With this configuration, the sequential lighting in the first light emitting unit and the lighting start in the second light emitting unit are controlled in accordance with the common timing signal.

In the light source lighting circuit of the second invention, the second light emitting unit may include a plurality of light sources, and the second lighting circuit may be configured to start sequential lighting of the light sources in the second light emitting unit in accordance with the timing signal.

With this configuration, the sequential lighting of the light sources in the second light emitting unit starts at appropriate timing, following the sequential lighting of the light sources in the first light emitting unit.

In the light source lighting circuit of the second invention, the first lighting circuit and the second lighting circuit may be configured to receive current from a common electric power supply line and to turn on the corresponding light sources, the first lighting circuit may be configured to generate a state signal corresponding to drive current flowing to the light sources of the first light emitting unit and to output a notification signal corresponding to the state signal to the second lighting circuit, the second lighting circuit may stop operation thereof or reduce a current value of regulating current flowing to a current consuming unit configured to consume a part of electric power to be supplied from the electric power supply line when the notification signal indicates an abnormality, and the first lighting circuit may be configured to output the timing signal through an output line of the notification signal.

With this configuration, it is not necessary to provide a separate output line of the timing signal in the configuration of stopping the operation of the second lighting circuit or reducing the current value of the regulating current, in correspondence to occurrence of the disconnection in the first light emitting unit.

In the light source lighting circuit of the second invention, preferably, the first lighting circuit includes a first DC/DC converter having a first switching element, and the second lighting circuit includes a second DC/DC converter having a second switching element.

The DC/DC converter has a relatively less amount of heat generation.

Also, a turn signal lamp of the second invention includes a first lamp unit attached to a door part provided to be freely openable and closable for a vehicle main body part at a rear end portion of a vehicle, and a second lamp unit attached to the vehicle main body part-side and positioned at an outermore side than the first lamp unit in a width direction of the vehicle. The first lamp unit includes the first lighting circuit and the first light emitting unit of the light source lighting circuit of the second invention, and the second lamp unit includes the second lighting circuit and the second light emitting unit of the light source lighting circuit of the second invention.

With this configuration, it is possible to prevent a lighting operation from being destabilized in the turn signal lamp where the respective lamp units are dispersedly arranged at the vehicle main body part and the door part.

Also, a light source lighting circuit of the third invention for achieving the first object is a light source lighting circuit provided with a first lighting circuit configured to receive current from an electric power supply line and to supply drive current to a first light source and a second lighting circuit configured to receive current from the electric power supply line and to supply drive current to a second light source, and includes a first current consuming unit provided for the first lighting circuit and configured to consume a part of the electric power to be supplied from the electric power supply line and to enable first regulating current to flow. The first lighting circuit is configured to generate a first state signal corresponding to a state of the drive current flowing to the first light source and to output a second notification signal corresponding to the first state signal to the second lighting circuit, and the second lighting circuit is configured to generate a second state signal corresponding to a state of the drive current flowing to the second light source and to output a first notification signal corresponding to the second state signal to the first lighting circuit. When the first state signal indicates an abnormality or when the first notification signal indicates an abnormality, the first lighting circuit lowers a current value of the first regulating current.

With this configuration, a difference between the supply current values through a common electric power supply line in a normal state where both the lamp units are not disconnected and in a disconnection state where at least one lamp unit is disconnected is increased.

The light source lighting circuit of the third invention may keep the first lighting circuit at a state where a light emission driving of the first light source is possible when the first state signal does not indicate an abnormality even though the first notification signal indicates an abnormality.

With this configuration, the lamp unit in which the disconnection has not occurred is kept at a state where the lighting circuit can turn on the light source in correspondence to the electric power supply from the electric power supply line.

The light source lighting circuit of the third invention may be provided with only the first current consuming unit, as a current consuming unit.

With this configuration, the number of the current consuming units provided for the vehicle lamp is minimized.

The light source lighting circuit of the third invention may include a second current consuming unit provided for the second lighting circuit and configured to consume a part of the electric power to be supplied from the electric power supply line and to enable second regulating current to flow, the first lighting circuit may be configured to output a second notification signal corresponding to the first state signal to the second lighting circuit, and the second lighting circuit may lower a current value of the second regulating current when the second state signal indicates an abnormality or when the second notification signal indicates an abnormality.

With this configuration, the current consuming units are dispersedly arranged in the two lamp units.

In the light source lighting circuit of the third invention, preferably, the first lighting circuit includes a first DC/DC converter having a first switching element, and the second lighting circuit includes a second DC/DC converter having a second switching element.

The DC/DC converter has a relatively less amount of heat generation.

Also, a turn signal lamp of the third invention includes a first lamp unit attached to a door part provided to be freely openable and closable for a vehicle main body part at a rear end portion of a vehicle, and a second lamp unit attached to the vehicle main body part-side and positioned at an outermore side than the first lamp unit in a width direction of the vehicle. The first lamp unit includes a first light emitting unit and the first lighting circuit of the light source lighting circuit of the third invention, and the second lamp unit includes a second light emitting unit and the second lighting circuit of the light source lighting circuit of the third invention.

With this configuration, it is possible to appropriately perform the disconnection determination for the turn signal lamp in which the respective lamp units are dispersedly arranged at the vehicle main body part and the door part.

Also, since a light emitting frequency of the turn signal lamp is relatively low, a chance that the electric power will be consumed by the current consuming unit is also relatively low.

Also, a light source lighting circuit of the fourth invention for achieving the third object is a light source lighting circuit provided for a pair of lamps of which electric power supply from a vehicle-side is individually controlled, and includes a light source driving unit configured to enable drive current to flow to a light source on the basis of the electric power to be supplied from the vehicle-side, a current consuming unit configured to consume a part of the electric power to be supplied from the vehicle-side and to enable regulating current to flow, and a current regulation circuit configured to receive a drive state signal corresponding to a state of the drive current and a mode signal indicative of a lighting/lights-out state of the other lamp from the other lamp and to lower a current value of the regulating current in each of a case where the drive state signal indicates an abnormality and a case where the mode signal indicates a lighting state.

With this configuration, in each of the pair of lamps, the current value of the regulating current is lowered when the lamp is in a disconnection state. Thereby, a difference between the supply current values from the vehicle-side (ECU-side) is increased. That is, when one of the lamps is turned on such as turn lighting, it is possible to appropriately perform the disconnection determination by the ECU of the related art based on the assumption of an incandescent lamp.

Further, according to the above configuration, when the pair of lamps is turned on at the same time, the electric power consumption in both the lamps is reduced as the current value of the regulating current is lowered. That is, it is possible to reduce the electric power consumption in both the lamps, in correspondence to a case where the simultaneous lighting such as hazard lighting is periodically repeated (or the simultaneous lighting may continue) for a relatively long time period.

In the light source lighting circuit of the fourth invention, the current regulation circuit may be configured to use the mode signal for regulating the regulating current via an insulation-type signal transmission element.

With this configuration, when an abnormality such as a shortcut occurs in a transmission path of the mode signal, it is possible to exclude an influence of the abnormality. Also, it is possible to block an extraneous noise occurring in the transmission path, so that it is possible to prevent a malfunction caused due to the noise.

Also, a turn signal lamp of the fourth invention may include the light source lighting circuit and the light source of the fourth invention, and the light source lighting circuit may be configured to branch a power supply voltage to be supplied from the vehicle-side and to output the same to the other lamp, as a mode signal indicative of a lighting/lights-out state of the lamp.

With this configuration, it is possible to reduce the power consumption and the amount of heat generation upon the hazard lighting. Also, a configuration for notifying whether or not it is a lighting state between both the lamps can be made by the configuration of branching and outputting the power supply voltage from the vehicle-side. Effects of the Invention

According to the first or third invention, it is possible to appropriately perform the disconnection determination for the vehicle lamp having the first lamp unit and the second lamp unit each of which is configured to receive the electric power to be supplied from the common electric power supply line.

According to the second invention, it is possible to prevent a deviation from occurring in connection of the sequential lighting from the first light emitting unit to the second light emitting unit.

According to the fourth invention, while it is possible to perform the disconnection determination at the vehicle-side upon the lighting of one lamp for the pair of lamps of which the electric power supply from the vehicle-side is individually controlled, it is possible to reduce the power consumption and the amount of heat generation when both the lamps are turned on at the same time, to decrease a possibility that a battery will be dead in the vehicle, and to reduce the manufacturing cost of the lamp.

Brief description of the drawings

FIG. 1 illustrates an example of a turn lamp system in which lighting control and disconnection determination are performed for a turn signal lamp.

FIG. 2 illustrates an outward configuration of a turn signal lamp of an illustrative embodiment.

FIG. 3 depicts a configuration outline of a turn lamp system of an illustrative embodiment.

FIG. 4 illustrates influences of fluctuation and variation in supply current value from a port of an ECU.

FIG. 5 illustrates an action that is to be obtained when adopting a method of a first illustrative embodiment.

FIG. 6 is a circuit diagram depicting a circuit configuration in the turn signal lamp having a light source lighting circuit of the first illustrative embodiment.

FIG. 7 is a circuit diagram for illustrating a modified embodiment of the first illustrative embodiment.

FIG. 8 depicts waveform diagrams of an input voltage (turn power supply) from a turn lamp ECU, a supply current value to an inner lamp unit and a supply current value to the outer lamp unit upon sequential lighting.

FIG. 9 is a circuit diagram depicting a circuit configuration in a turn signal lamp having a light source lighting circuit of a second illustrative embodiment.

FIG. 10 is a circuit diagram for illustrating a modified embodiment of the second illustrative embodiment.

FIG. 11 illustrates an action that is to be obtained when adopting a method of using regulating current.

FIG. 12 is a circuit diagram depicting a circuit configuration in a turn signal lamp having a light source lighting circuit of a third illustrative embodiment.

FIG. 13 is a circuit diagram depicting a circuit configuration in a turn signal lamp having a light source lighting circuit of a first modified embodiment of the third illustrative embodiment.

FIG. 14 is a circuit diagram depicting a circuit configuration in a turn signal lamp having a light source lighting circuit of a second modified embodiment of the third illustrative embodiment.

FIG. 15 illustrates a light source lighting circuit and a turn signal lamp of a fourth illustrative embodiment.

FIG. 16 illustrates a current regulation circuit of the fourth illustrative embodiment. DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS First Illustrative Embodiment

Hereinafter, a turn signal lamp having a light source lighting circuit of an illustrative embodiment will be described with reference to the accompanying drawings.

Meanwhile, in below descriptions, “turn signal lamp” is abbreviated to “turn lamp”.

First, an example of a turn lamp system configured to perform lighting control and disconnection determination for a left and front turn lamp FtL, a right and front turn lamp FtR, a left and rear turn lamp BtL and a right and rear turn lamp BtR is described with reference to FIG. 1 .

The system is provided with a turn lamp ECU (Electronic Control Unit) 100 for performing lighting control and disconnection determination for the turn lamps FtL, FtR, BtL, BtR. The turn lamp ECU 100 has four ports of ports p 1 to p 4 , and the left and front turn lamp FtL is connected to the port p 1 , the right and front turn lamp FtR is connected to the port p 2 , the left and rear turn lamp BtL is connected to the port p 3 and the right and rear turn lamp BtR is connected to the port p 4 , as shown.

The turn lamp ECU 100 is configured to input an output voltage B (hereinafter, referred to as “battery voltage B: 12V, in the first illustrative embodiment) from an in-vehicle battery and to ON/OFF control (for example ON=350 ms, OFF=350 ms) a supply of the battery voltage B to the turn lamps FtL, FtR, BtL, BtR connected to the ports p 1 , p 2 , p 3 , p 4 with a predetermined period, in response to an operation of a winker lever, a hazard switch or the like (not shown), for example, thereby performing lighting control (blinking control) of the turn lamps FtL, FtR, BtL, BtR.

Also, the turn lamp ECU 100 is configured to detect a current value from the port p for a time period in which the supply of the battery voltage B is ON and to determine whether the detected current value is below a predetermined threshold value, for each port p, thereby performing disconnection determination for each of the turn lamps FtL, FtR, BtL, BtR.

At this time, the turn lamp ECU 100 is configured to set an ON/OFF period of the battery voltage B to be supplied shorter than a usual state (a state where disconnection does not occur) for the turn lamp for which a disconnection state is determined (for example, sets an OF/OFF frequency substantially two times higher than the usual state).

FIG. 2 illustrates an outward configuration of the left and rear turn lamp BtL and the right and rear turn lamp BtR of the illustrative embodiment. Meanwhile, in FIG. 2 , the outward configuration of the left and rear turn lamp BtL is depicted by a schematic front view. In the meantime, the outward configuration of the right and rear turn lamp BtR is bilaterally symmetric to the outward configuration of the left and rear turn lamp BtL shown in FIG. 2 and is not shown.

The left and rear turn lamp BtL includes an inner lamp unit 1 provided in an inner housing C 1 and an outer lamp unit 2 provided in an outer housing C 2 . The outer housing C 2 is arranged closely to an outer side in a width direction of a vehicle (a vehicle width direction) with respect to the inner housing C 1 . In this case, the inner lamp unit 1 is attached to a door part (for example a trunk lid or a rear hatch door) provided to be freely openable and closable for a vehicle main body part at a rear end portion of the vehicle, and the outer lamp unit 2 is attached to the vehicle main body part-side.

FIG. 3 depicts a configuration outline of the turn lamp system in which the left and rear turn lamp BtL and the right and rear turn lamp BtR each of which has the inner lamp unit 1 and the outer lamp unit 2 are used.

In the turn lamp system of the first illustrative embodiment, the turn lamp ECU 100 having the four ports shown in FIG. 1 is used. In the turn lamp ECU 100 , the inner lamp unit 1 and the outer lamp unit 2 configuring the left and rear turn lamp BtL are connected to the port p 3 , and the inner lamp unit 1 and the outer lamp unit 2 configuring the right and rear turn lamp BtR are connected to the port p 4 . That is, the inner lamp unit 1 and the outer lamp unit 2 configuring the left and rear turn lamp BtL are configured to enable light sources to emit lights on the basis of electric power to be supplied from the common port p 3 , and the inner lamp unit 1 and the outer lamp unit 2 configuring the right and rear turn lamp BtR are configured to enable light sources to emit lights on the basis of electric power to be supplied from the common port p 4 .

Herein, for the turn lamp having the two lamp units as described above, a disconnection state is determined when disconnection occurs in at least one of the two lamp units. Specifically, the turn lamp ECU 100 is configured to perform the disconnection determination for the left and rear turn lamp BtL and the right and rear turn lamp BtR by determining whether a supply current value from each of the ports p 3 , p 4 is below a threshold value, which is set in correspondence to a supply current value when one of the inner lamp unit 1 and the outer lamp unit 2 is disconnected.

At this time, however, it cannot be said that the supply current value from the port p is always constant. Specifically, the supply current value from the port p fluctuates in association with fluctuation in the battery voltage B. Also, the supply current value from the port p may be varied due to factors such as variation in voltage/current of a light source configuring the turn lamp, a difference of a light emission driving circuit configuration of the light source (for example, when a switching power supply circuit such as a DC/DC converter (which will be described later) is used for the light emission driving circuit, variation in input current value in association with variation in the battery voltage B is relatively large), and the like.

FIG. 4 illustrates influences of fluctuation and variation in the supply current value from the port p, and pictorially depicts, as change characteristics of the supply current value (input current value) of one port with respect to change in the battery voltage B, a change characteristic h 1 in a normal state where both the inner lamp unit 1 and the outer lamp unit 2 are not disconnected and a change characteristic h 2 in a disconnection state where any one of the inner lamp unit 1 and the outer lamp unit 2 is disconnected.

Meanwhile, in FIG. 4 , vertical widths of the change characteristics h 1 , h 2 indicate widths of the variations. Also, a fluctuation range of the battery voltage B is a range of 10V to 16V, for example.

In order to perform the disconnection determination, a determination threshold value th should be set between a lower limit value Ld of the supply current value in the normal state indicated by the change characteristic h 1 and an upper limit value Lu of the supply current value in the disconnection state where any one of the inner lamp unit 1 and the outer lamp unit 2 is disconnected, which is indicated by the change characteristic h 2 .

However, the lower limit value Ld and the upper limit value Lu may come close to each other due to the fluctuation and variation and a difference thereof may be reduced. Also, in some cases, the lower limit value Ld and the upper limit value Lu may lap each other. In the case where the lower limit value Ld and the upper limit value Lu lap each other, it is not possible to perform the disconnection determination even when any threshold value th is set. Also, in the case where the lower limit value Ld and the upper limit value Lu come close to each other, it is not possible to perform the disconnection determination if a difference between the two values is small. In order to perform the disconnection determination by using the threshold value th, it is necessary to secure a margin M (for example, a margin of about ±0.25 A on the basis of the threshold value th), based on the detection precision of the supply current value. In a case where the difference between the upper limit value Lu and the lower limit value Ld is less than the margin M, both the values are detected as equal, so that it is not possible to appropriately perform the disconnection determination (in FIG. 4 , an example where the difference between the upper limit value Lu and the lower limit value Ld is less than the margin M is shown).

The description continues in the full USPTO document.